Most industrial and automotive internal combustion engines include a pair of cylinder banks, each including a plurality of cylinders. For example, a V-8 engine includes two banks of four cylinders each. With the advent of electronic controls, the operating conditions of each of the cylinders and of each bank of cylinders is controlled by an on-board engine control computer or an electronic controller. The typical electronic controller provides signals to electrically actuated fuel control systems, firing timing systems and air intake systems. In diesel engines, the electronic controller performs the critical task of controlling the timing of operation of the fuel injectors to ensure optimum combustion performance. The electronic controller also acts as a speed governor, accepting input from the accelerator pedal and sensing engine load conditions to establish an engine speed.
One problem encountered by internal combustion engines is excessive vibration and imbalanced loads applied to the engine crankshaft and output shaft. Of course, excessive vibration, particularly at engine idle, is felt, and heard, by the vehicle operator. However, the most significant risk created by engine vibration is borne by the engine itself, particularly the crankshaft and bearings. Engine vibration is known to significantly decrease the fatigue life of engine components. Moreover, engine vibration can decrease the overall engine performance, especially under critical duty cycles.
One source of engine vibration is imbalanced power output from each bank of cylinders. Ideally, opposed banks of cylinders will generate identical power output levels for identical operating conditions (i.e.--fuel quantity, injection timing, air intake). Of course, mechanical losses in each bank will be different, and the operating conditions will usually differ between banks. Unless these different mechanical losses and operating conditions are accounted for, the opposing cylinder banks will necessarily generate different power output levels.
Similar problems exist in power generation systems, for example, that utilize a plurality of engines to drive a generator. In these systems, the power output from each engine is combined by a transmission mechanism to a common output shaft. In this arrangement, power imbalance between engines can still generate vibration and fatigue problems in the transmission mechanism and common output shaft. Thus, balancing the power generated by each engine can be as important as balancing power output between opposing cylinder banks of the same engine.
While some attempt has been made to address drive shaft speed variations from cylinder to cylinder, no approach has been developed that will address the power imbalance conditions discussed above. A need therefore exists for a system and method that can readily detect power imbalance between opposing cylinder banks of an engine, as well as for power imbalances between multiple engines combined to a single output.